U.S. Pat. Nos. 4,942,700 and 5,024,031, hereby incorporated by reference as if fully disclosed herein, disclose a method for constructing reversibly expandable truss-structures in a wide variety of shapes and the teachings therein have been used to build structures for diverse applications including architectural uses, public exhibits and unique folding toys.
In accordance with the teaching of the '700 patent, the resulting structures comprise substantially linear, but angulated, strut elements and smaller hub elements that are pivotally connected. The angulated struts always have three pivot points, one central pivot point and two terminal pivot points, and they lie in planes that are essentially orthogonal to the surface of the structure. Utilizing the methods taught in the '700 patent, one may construct foldable structures in a wide variety of shapes. However, certain shapes are more practical to construct in order to maintain a reasonable part count, have good structural integrity and ease of movement. In particular, the method is better suited to structures whose shape has a gentle curvature, rather than sharp corners. Also, the parts that make up a given structural shape will, in general, be unique to that particular shape. Therefore, it is not a simple matter to make a kit of interchangeable parts that may be used in different shaped structures.